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75 lines
2.7 KiB
Python
75 lines
2.7 KiB
Python
from functools import lru_cache
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from typing import Dict, FrozenSet, Iterable, List, Optional, Union
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import torch
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from transformers import PreTrainedTokenizer
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from vllm.sampling_params import LogitsProcessor
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class AllowedTokenIdsLogitsProcessor:
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"""Logits processor for constraining generated tokens to a
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specific set of token ids."""
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def __init__(self, allowed_ids: Iterable[int]):
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self.allowed_ids: Optional[List[int]] = list(allowed_ids)
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self.mask: Optional[torch.Tensor] = None
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def __call__(self, token_ids: List[int],
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logits: torch.Tensor) -> torch.Tensor:
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if self.mask is None:
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self.mask = torch.ones((logits.shape[-1], ),
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dtype=torch.bool,
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device=logits.device)
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self.mask[self.allowed_ids] = False
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self.allowed_ids = None
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logits.masked_fill_(self.mask, float("-inf"))
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return logits
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@lru_cache(maxsize=32)
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def _get_allowed_token_ids_logits_processor(
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allowed_token_ids: FrozenSet[int],
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vocab_size: int,
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) -> LogitsProcessor:
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if not allowed_token_ids:
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raise ValueError("Empty allowed_token_ids provided")
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if not all(0 <= tid < vocab_size for tid in allowed_token_ids):
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raise ValueError("allowed_token_ids contains "
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"out-of-vocab token id")
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return AllowedTokenIdsLogitsProcessor(allowed_token_ids)
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def get_logits_processors(
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logit_bias: Optional[Union[Dict[int, float], Dict[str, float]]],
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allowed_token_ids: Optional[List[int]],
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tokenizer: PreTrainedTokenizer) -> List[LogitsProcessor]:
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logits_processors = []
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if logit_bias:
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try:
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# Convert token_id to integer
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# Clamp the bias between -100 and 100 per OpenAI API spec
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clamped_logit_bias: Dict[int, float] = {
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int(token_id): min(100.0, max(-100.0, bias))
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for token_id, bias in logit_bias.items()
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}
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except ValueError as exc:
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raise ValueError(
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"Found token_id in logit_bias that is not "
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"an integer or string representing an integer") from exc
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def logit_bias_logits_processor(token_ids: List[int],
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logits: torch.Tensor) -> torch.Tensor:
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for token_id, bias in clamped_logit_bias.items():
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logits[token_id] += bias
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return logits
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logits_processors.append(logit_bias_logits_processor)
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if allowed_token_ids is not None:
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logits_processors.append(
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_get_allowed_token_ids_logits_processor(
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frozenset(allowed_token_ids), tokenizer.vocab_size))
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return logits_processors
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